Day18-Operation_Order

Oper <- read.csv("day18.csv", sep = "\n",header = FALSE)
Oper <- as.character(Oper[,1])

CalculateExpression <- function(CurrOp) {

    CurrOp <- gsub(" ", "", CurrOp)
    CurrOp <- unlist(strsplit(CurrOp, ""))

    while (length(CurrOp)>1 ) {

        PosOpen <- which(CurrOp == "(")
        PosClose <- which(CurrOp == ")")

        n <- length(PosOpen)

        InnerClose <- ifelse(n==0, length(CurrOp), min(PosClose)-1)
        InnerOpen <- ifelse(n==0, 1, max(PosOpen[PosOpen < min(PosClose)])+1)

        InnerOp <- CurrOp[InnerOpen:InnerClose]
        
        while (length(InnerOp) > 1) {
            CurrRes <- ifelse(InnerOp[2] == "+", as.numeric(InnerOp[1])+as.numeric(InnerOp[3]), 
                                                 as.numeric(InnerOp[1])*as.numeric(InnerOp[3]))
            if (length(InnerOp)>=4) {
                InnerOp <- c(as.character(CurrRes), InnerOp[4:length(InnerOp)])
            } else {
                InnerOp <- as.character(CurrRes)
            }
        }

        if (InnerOpen == 1 & InnerClose == length(CurrOp)) {
            CurrOp <- as.character(CurrRes)
        } else {
        if ((InnerClose+1)==length(CurrOp)) {
            CurrOp <- c(CurrOp[1:(InnerOpen-2)], as.character(CurrRes))
        } else {
        if ((InnerOpen-1)==1) {
            CurrOp <- c(as.character(CurrRes), CurrOp[(InnerClose+2):length(CurrOp)])
        } else {
            CurrOp <- c(CurrOp[1:(InnerOpen-2)], as.character(CurrRes), CurrOp[(InnerClose+2):length(CurrOp)])   
        }}}
    }

    FinalResult <- as.numeric(CurrRes)
    return(FinalResult) 
}

ResultsOper <- rep(NA, length(Oper))
ResultsOper <- unname(sapply(Oper, CalculateExpression))
format(sum(ResultsOper), scientific = FALSE)

# Part 2: New math rules

CalculateExpressionUnderNewRules <- function(CurrOp) {
    
    CurrOp <- gsub(" ", "", CurrOp)
    CurrOp <- unlist(strsplit(CurrOp, ""))
    
    while (length(CurrOp)>1 ) {
        
        PosOpen <- which(CurrOp == "(")
        PosClose <- which(CurrOp == ")")
        
        n <- length(PosOpen)
        
        InnerClose <- ifelse(n==0, length(CurrOp), min(PosClose)-1)
        InnerOpen <- ifelse(n==0, 1, max(PosOpen[PosOpen < min(PosClose)])+1)
        
        InnerOp <- CurrOp[InnerOpen:InnerClose]
        
        while (length(InnerOp) > 1) {
            Multies <- which(InnerOp == "*")
            Addies <- which(InnerOp == "+")
            
            ThisFirst <- ifelse(length(Addies) == 0, min(Multies), min(Addies))
            
            CurrRes <- ifelse(InnerOp[ThisFirst] == "+", 
                              as.numeric(InnerOp[ThisFirst-1])+as.numeric(InnerOp[ThisFirst+1]), 
                              as.numeric(InnerOp[ThisFirst-1])*as.numeric(InnerOp[ThisFirst+1]))
            
            if (length(InnerOp)<4) {
                InnerOp <- as.character(CurrRes)
            } else {
            if (ThisFirst == 2) {
                InnerOp <- c(as.character(CurrRes), InnerOp[(ThisFirst+2):length(InnerOp)])
            } else {
            if (ThisFirst == (length(InnerOp)-1)) {
                InnerOp <- c(InnerOp[1:(ThisFirst-2)], as.character(CurrRes))
            } else {
                InnerOp <- c(InnerOp[1:(ThisFirst-2)], as.character(CurrRes), InnerOp[(ThisFirst+2):length(InnerOp)])
            }}}
        }
        
        if (InnerOpen == 1 & InnerClose == length(CurrOp)) {
            CurrOp <- as.character(CurrRes)
        } else {
        if ((InnerClose+1)==length(CurrOp)) {
            CurrOp <- c(CurrOp[1:(InnerOpen-2)], as.character(CurrRes))
        } else {
        if ((InnerOpen-1)==1) {
            CurrOp <- c(as.character(CurrRes), CurrOp[(InnerClose+2):length(CurrOp)])
        } else {
            CurrOp <- c(CurrOp[1:(InnerOpen-2)], as.character(CurrRes), CurrOp[(InnerClose+2):length(CurrOp)])   
        }}}
    }
    
    FinalResult <- as.numeric(CurrRes)
    return(FinalResult) 
}

ResultsNewOper <- rep(NA, length(Oper))
ResultsNewOper <- unname(sapply(Oper, CalculateExpressionUnderNewRules))
format(sum(ResultsNewOper), scientific = FALSE)